In the design and operation of nozzles of the type used in fire fighting, there are a number of difficult problems to solve. One of these problems lies in the fact that, when the quantity of fluid is changed, force couples may be generated to make the nozzle difficult to handle. Such force couples can be produced by a non-symmetrical flow of fluid passing through the nozzle. Attempts to overcome these difficulties in the past have resulted in very complex and expensive mechanisms which were easily rendered inoperative and which were subject to a considerable amount of maintenance. The main problem, however, lies in the fact that, so far as generating foam is concerned, there is only one flow rate at which the foam is most effectively formed. In the past, it has been common practice to use a single tube nozzle and to change the flow rate simply by using one, two, or three apertures or orifices, as the demand called for greater flow. If the apparatus was designed for the most effective formation of foam with one aperture, then, when more than one aperture was used, the foam generated was inadequate. In order to overcome this difficulty, some nozzles are designed with a plurality of tubes and the quantity of fluid was determined by using one, two, or more of the tubes. While each tube generates the foam effectively, unfortunately it is necessary for at least one of the tubes to be spaced from the pivotal axis of the nozzle and the force couple set up is extremely great, making it difficult to control the direction in which the nozzle is pointed. An indication of the order of magnitude of forces developed can be understood when it is known that, when a flow of 2400 gallons per minute takes place at 200 psi, the force developed is 1700 lbs. While many nozzles have their turning and directional stability controlled with a power assist of a hydraulic type, a force couple requires the use of larger and more expensive equipment. Furthermore, there are instances when the nozzle must be manipulated manually. At that time the force couple generated at high flow rates makes the nozzle very difficult (and even hazardous) to handle. These and other difficulties experienced with the prior art devices have been obviated in a novel manner by the present invention.
It is, therefore, an outstanding object of the invention to provide a nozzle capable of operation at high flow rates with effective generation of foam, but with no appreciable force couple about the nozzle pivot.
Another object of this invention is the provision of a nozzle in which the flow rate can be increased in multiples of a base flow rate by a simple manipulation.
A further object of the present invention is the provision of a nozzle in which the generation of foam remains the same at flow rates which are multiples of a base flow rate.
It is another object of the instant invention to provide a nozzle for the generation of foam whose construction is simple, which can be easily manufactured from readily available materials, and which is capable of a long life of useful service with a minimum of maintenance.
With these and other objects in view, as will be apparent to those skilled in the art, the invention resides in the combination of parts set forth in the specification and covered by the claims appended hereto.